Investigation of the Effects of Functional Groups on the Inhibition Performances of Imidazolium-Based Bola-Form Ionic Liquids as Novel High-Performance Shale Inhibitors

Ionic liquids (ILs) are considered effective additives to inhibit shale hydration swelling in recent years. The imidazolium-based bola-form ionic liquids (IBFILs) with two positively charged groups and optimal alkyl chain lengths can greatly enhance their electrostatic interaction with clay to improve their inhibition ability. The present study further extends our previous research on IBFILs to investigate the effects of different modified functional groups on the inhibition properties of three novel IBFILs including [C6(BIM)2]­Br2, [C6(NBIM)2]­Br2, and [C6(ABIM)2]­Br2. Then, their inhibition performances are evaluated via immersion tests, linear swelling tests, and hot-rolling recovery tests. The inhibition properties of three novel IBFILs are evidently improved in different degrees, especially for the [C6(ABIM)2]­Br2 with amine groups. Then, the inhibition mechanisms are analyzed via contact angle measurements, Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), particle size distribution measurement, ζ-potential, and molecular electrostatic potential (MEP) distribution. The results reveal that the hydrogen bonding and protonation of amine groups should be responsible for the outstanding inhibition property of [C6(ABIM)2]­Br2, whereas the nitro groups indirectly hinder the coverage of the benzene rings at the clay surface to partially affect the inhibition capacity of [C6(NBIM)2]­Br2. Finally, the proposed mechanisms are further confirmed by molecular dynamics simulations. Our work may provide novel insight into the development and design of efficient IL inhibitors with modified functional groups.